1. Field of the Invention
The present invention relates to an improved suspension system for supporting the body of a vehicle.
2. Description of Relevant Art
In Japanese Patent Publication No. 51-21218 (76-21218) there is disclosed a vehicle body suspension system which comprises a hydraulic oil damper wherein a piston rod, which is coupled to a piston received within a cylinder, is formed with an oil channel extending axially therethrough. The piston rod has an upper end connected to the vehicle body by means of an annular elastic member made of rubber or the like and arranged concentrically of the piston rod. An oil chamber is provided which has a portion of its peripheral wall formed by an upper surface of the elastic member, and such oil chamber communicates with the interior of the cylinder through the axial oil channel in the piston rod. The hydraulic oil damper is thus arranged such that the static load of the vehicle body acts upon the oil filled within the hydraulic oil damper to thereby reduce the force being directly applied to the elastic member. In accordance with such suspension system, the space above the elastic member which formerly was not utilized in prior known systems of such type is utilized for the variable volume oil chamber which accommodates oil overflowing from the cylinder to render the entire system compact in size. Further, the oil pressure within such oil chamber acts upon the elastic member so as to urge its upper surface against the upward movement of the piston rod so as to restrain deformation of the elastic member and thus increase the wear life of the elastic member.
The above-described known suspension system suffers from the following disadvantages.
First, because the high oil pressure within the cylinder acts directly upon the elastic member through the oil channel in the piston rod during contraction of the hydraulic oil damper which is due to an increased load applied to the vehicle body, the elastic member is still subjected to a large amount of deformation, resulting in extensive damaging or deterioration of the elastic member and its peripheral oil seals. Secondly, although in the aforesaid known suspension system the height of the vehicle body can be adjusted by varying the amount of oil charged within the interior of the system, the internal oil pressure has to be elevated to a very high value to obtain a relatively large height of the vehicle body, which may result in oil leakage. Thirdly, due to the aforesaid high internal oil pressure, strict machining tolerances are required for the piston, the cylinder, etc., which may lead to a complex construction of the system.